Method and means for the control of emulsion heat



A ril 21, 1953 D. DALlN ETAL 2,635,315

METHOD AND MEANS FOR THE CONTROL OF EMULSION HEAT Filed April 11, 1949 INVENTORS ATTORIXQY Patented Apr. 21, 1953 P METHOD AND MEANS FOR THE CONTROL OF EMULSION HEAT David Dalin, Ronninge, and Tore J. Hedbiick, Sodertalje, Sweden, assignors to AB Svenska Maskinverken, Sodertalje, Sweden, a corpora.-

tion of Sweden Application April 11, 1949, Serial No. 86,842 In Sweden April 14, 1948 2 Claims.

'This invention relates to method and apparatus for heating by indirect heat exchange, and

' refers more particularly to a method and apparatus for accurately and individually controlling the temperatures obtainable from each of several secondary heat exchangers supplied from V a common primary heat exchanger.

The copending application of David Dalin, Serial No, 868, filed January '7, 1948, now Patent No. 2,532,608, relates to the use of steam-water emulsion to maintain a constant temperature at a secondary heat exchanger and utilizes the fact f that the sensible temperature of a steam-water emulsion will remain constant, so long as its form remains that of an emulsion at constant pressure, regardless of the fact that the relativ proportions of steam and water comprising the emulsion may be changed. In the method and apparatus of said copending application control of the temperature is effected in a central steam generating boiler by regulating the pressure (and 1 consequently the temperature) at which the emulsion is generated, and at which it is substantlally maintained throughout the system.

However, there are numerous applications in which such common control is insufiicient and 3 in which it is desirable to individually control the temperatures at each of the several seei ondary heat exchangers through which the fluid is passed in its circuit and at which it gives up heat. Numerous examples of such applications are to be found in the chemical and food processing industries, as well as many others which will readily suggest themselves.

The present invention has for its principal object a method and means for carrying out such 1 control.

Another object of this invention resides in the provision of a method and means for individually regulating the temperatures of each of a number. of radiators, all supplied with heat exchange fluid from a common boiler, and maintaining a prej, determined temperature at each, which temperature may be the steaming temperature of the fluid or any lower temperature. 7 Still another object of this invention resides thereby minimize heat losses in the system;

The invention is described in greater detail panying drawing, in which Fig. 1 is a diagrammatic illustration of one type of apparatus suitable for carrying out the method of this invention; and Fig. 2 is a diagrammatic view of a detail of the apparatus, namely the separator.

Referring now to the accompanying drawing, the numeral I designates a tubular steam boiler or primary heat exchanger which, as is customary, may be situated in a combustion chamber or flue gas pass of a boiler plant (not shown) and in which boiler fluid is adapted to be heated to a steam-water emulsion. The inlet of the boiler or primary heat exchanger is connected with a steam dome 2 by means of a conduit 3, and water from the steam dome is forcibly circulated through the boiler, as well as the remainder of the system, in the direction of the arrows a, by means of a circulating pump 4 connected in the line 3 between the boiler and the steam dome. The outlet of the boiler is connected with one or more secondary heat exchangers 5 at which the circulating fluid gives off to a medium to be heated a substantial portion of the heat received at the boiler.

The secondary heat exchange apparatus 5 is not connected directly to the boiler however. Instead, steam-water emulsion generated in the boiler is first introduced, through a communicating duct l6, into steam separators 6, one for each heat exchanger, where the emulsion may be wholly or partly separated into its liquid and vapor components. A conduit 8 communicates the upper portion of each steam separator with the output conduit IU of the heat exchangers or radiators 5 to thus provide a bypass around the heat exchangers for a predetermined proportion of the steam component of the emulsion; and, as will be seen presently, this bypassed portion of the steam component carries so much of the heat value of the emulsion as is not required at the radiator. The hot water, together with so much of the steam component of the emulsion as is not bypassed around the radiator, leaves the bottom of each of the steam separators through a conduit [1 which connects with the inlet 1 of one of the secondary heat exchangers.

A control valve I2 is situated at the inlet of each of the steam separators, so that adjustment of the several valves l2 will enable regulation of the relative proportion of the generated emulsion admitted to each of the separators, and thus to each of the heat exchangers. A control valve l3 in the bypass duct 8 which connects the steam outlet of each steam separator with the outlet ID of its associated secondary heat exchange apparatus regulates the rate at which steam is bypassed around the radiators and thus enables a greater or lesser proportion of steam to be admixed with the hot water circulated through the secondary heat exchanger to thereby control the heat value of the fluid circulated through each 7 4 heat exchanger. Any one of the valves l2 may of course be closed completely to 'cut its associated steam separator and heat exchanger out of the system, and another. valve 14in the outlet conduit of each radiator may alsobe-closed to prevent back circulation, of. returning fluid through the radiator which has been shut off.

It will thus be seen that the circulating pump 4 pumps water under positive circulating" pressure from the steam dome to the boiler, through which it circulates the water at a rate. and under a pressure such that the water is heated to the point of partial vaporization, to thus generate a steam-wa-ter emulsion. This steam-wateremulsion is then conducted to the severallsteam separators, 'whereafter the water, mixed with some predetermined amount of steam, is conducted through the secondary heat exchange apparatus 5, while the remaining separated steam is bypassed through the conduits 8. As a result the secondary heat exchange apparatus 5 operates partially or exclusively with hot water, and the i temperature difference between the heat-absorbingpartsand the media to be heated isvariable because the hot water temperature is continu- I .ously sinking during the passage of the hot water through the apparatus. The quantitiesof liquid which may be caused to vpass through thesecondary heat-exchange apparatus 5, may be controlled by means of the valve l2. Bythrottling the by-pass conduit 8 more or less, by means of the valve l3, hot Water can be mixed withsteam bubbles in varying proportions sothat-thetemperature of the first part of the heatiabsorbing surface in the respective secondaryheat exchange apparatus may be held constant, 1. e. at

saturation: temperature, but, all steam having become condensed in the course of travel through the first part, the temperature. inthe latter part will successively sink because .all of the latentheat of condensation will have been abstracted from the fluid and it will begin to give up its sensible heat.- In order to insure the control of the emulsion and of the separated steam under all con- .ditions of load, the secondary heatlexchanger's 5 should be constructed with arelatively high. flow .The heat-absorbing surfaces 01', in other words, the heat-consumption apparatus should be designed in. such a, way that the. inlet and the outlet of the pipe coils are placed side by side, with the .coils run. parallel to one another for some distance. In thisway substantially the same temperature may be obtained at. all points onthe secondary heat exchanger; A further equalization of the temperature is obtained if the inlet and theoutlet of the pipe coils are. heat conductively connected. to

each other, e. g. by'fianges of heat-conductive material welded between them.

The steam separator canadvantageously. be

'mounted at those points of the emulsion pipe line where separated consumption steam is. re-

1 quired. In this case saidsteam-maybeiused-ior other purposes.

In the embodiment shown, the steam separator consists of a cylindrical vessel I 5, into the upper part of which the emulsion pipe line It opens tangentially to thus cause the emulsion to ,be quickly rotated in thevessel. The steam is separated from' the water at the top and the hot Water is collected at the bottom of the vessel, the

upper surface of the water becoming concave,

substantially as shown by the dash and dot line when asubstantial proportion of the steam is "being bypassed through the conduit 8. The hot water conduit I'Lleaves the lower part and the a steam by-pass. conduit 8 leaves the upper part 01.

.therse'condary heat exchanger.

been-opened sufli'ciently to permit only the liquid component of the emulsion to enter the inlet 01' If the valve is throttled to some extent, the pressure within the separator vessel willibuild up tothe point where steam :bubbleswillzbe forced into the-outlet: 11 along withthe liquid, and if the valve 13 is closed completely steam-water emulsion, asgenera ted in the boiler, will be circulated through the secondary heatexchanger.

Other media than-water, such as diphenox and mercury, may of course be used in practicing the invention.

Itwill thus be seen that by means of this invention the temperature output of each o1several secondary heat exchangers may be regulated within-very close limits by regulating the relative proportions of steam and hot water circulated througheach and by regulating the rate ofsuch circulation through each. Thus if said proportionsand rate are suchthat not all of the-steam is condensed at the-time the fluid reachesthe outlet, the temperature through the entire secondary heat exchanger will be substantially constant and will be equal to the steaming tempera- .ture of :water under the prevailing. pressure conditions. =On:the other hand, where therate of circulation of the water is predetermined and-the rate of heat abstraction therefrom is known; the outlet temperature of thewatermay be readily determined, and the mean temperatureobtained at the secondary heat exchanger during. the course of such circulation may likewise be readily determined and maintained. It followsthat any temperature may be accurately maintained at each of. the secondaryheat exchangers, fromthe steaming temperature of water under the-prevailing conditions in the heat exchange coils downwardly, and that the desired temperature may be achieved by adjustment of the control valves 12 and I3. It will be obvious that such regulation-may be separatelyeffected-for each of-the individual secondary heat exchangers, so that each of them may beoperating at a different temperature from .-:the others, andv maintaining that temperature constantly and accurately,- de- ..sp1te the :fact that all of the secondaryheatexchangers are supplied with heat exchange fluid from a common central source.

It willbe noted thatrecombination of the bypassed steam with the fluid which'has been circulated through the heat exchangers eiTects a saving of. the unused heat value of thatportion of.-the emulsion .represented by such steam.

From the foregoingdescription, togetherwith the accompanying drawings, it will be readily .apparent that the method and apparatus of'this -mvention,provides,.heating means whereby the temperature of each" of a numberof. heatersall supplied from a common central source, may be individually regulated with a high degree of accuracy and whereby the heat output of each may be accurately controlled and its temperature thus maintained at any desired value up to the steaming temperature of the fluid circulated therethrough.

Having now described our invention, what we claim as new and desire to secure by Letters Patent is:

1. The method of controlling the heat output of heat exchange fluid circulating in indirect heat exchange relation with a medium to be heated to thereby heat said medium to a predetermined temperature, which method comprises: forcibly circulating liquid heat exchange fluid in indirect heat exchange relation with a heat source at a temperature and under a pressure such as to convert the same to a liquid-vapor emulsion; centrifugally separating the liquid and vapor components of the emulsion; forcibly circulating the separated liquid component of the emulsion through a secondary heat exchanger in indirect heat exchange relation with medium to be heated; forcibly circulating a portion of the separated vapor component of said emulsion through said heat exchanger with the liquid component; and regulating the proportion of vapor circulated through said heat exchanger with said liquid to maintain the temperature of the fluid circulating therethrough at a predetermined mean value.

2. In apparatus of the type in which indirect heat transfer is effected between media to be heated and boiler fluid circulated in a closed system including a boiler and a plurality of radiators at which such heat transfer occurs, means for individually controlling the temperature of the radiators, comprising: means including a steam dome providing a source of liquid boiler fluid; means for forcibly circulating liquid boiler fluid from said source through the boiler at a rate and under a pressure such as to convert the fluid to a vapor liquid emulsion; a plurality of separators, one for each radiator, in each of which emulsion is adapted to be separated. into its liquid and vapor components, each having an inlet communicating with the outlet of the boiler, a vapor outlet near its top and another outlet near its bottom; duct means communicating said other outlet of each of said separators with the inlet of a radiator to enable the liquid component of emulsion in the separator to be circulated through the radiator together with a portion of the vapor component; duct means communicating the vapor outlet of each of the separators with the steam dome to enable separated vapor component to be bypassed around said radiators; means in said last named duct means for regulating the proportion of separated vapor component which is bypassed around the radiators from each separator to thus regulate the proportion of vapor component which is circulated through each radiator with the liquid component so that the fluid passed through each radiator will have a predetermined heat value corresponding to that of the generated emulsion introduced into its separator less that of the vapor component thereof which has been bypassed around the radiators; and means connecting the outlet of each of said radiators with the steam dome for returning the fluid circulated through the radiators to the steam dome.

DAVID DALIN. TORE J. HEDBiicK.

References Cited in the flle of this patent UNITED STATES PATENTS Number Name Date 311,606 Pratt Feb. 3, 1885 792,494 Bruckner June 13, 1905 2,532,608 Dalin Dec. 5, 1950 FOREIGN PATENTS Number Country Date 377,388 France Sept. 5, 1907 564,656 France Jan. 8, 1924 

